This invention relates to multi-speed power transmissions and, more particularly, to multi-speed power transmissions having two input clutches.
Dual input clutch transmissions are designed to permit engine power to be distributed through separate power paths depending upon which input clutch is engaged. During the engagement of one of the input clutches, and a power path which is completed by other clutches downstream in the power flow path, the second or oncoming power path can be preselected by moving or operating other clutches in the on-coming power path and then swapping the input clutches. This swapping procedure takes place through the forward speeds. For example, the first clutch is on in odd number ratios and the second clutch is on in even number ratios.
The dual clutch power transmissions have been primarily designed as countershaft-type transmissions. Countershaft-type transmissions are commonly termed manual transmissions in the transmission art. Each of these types of transmissions includes a synchronizer clutch or mechanical clutch for each of two gear ratios on each countershaft. The first of the input clutches connects the power path through a head gear set to a first countershaft and the second input clutch connects the head gear set to a second countershaft. The head gear set might be equal in ratio or different in ratio. The power paths then flow from their respective countershafts back to a main transmissions shaft, which is connected with the transmission output shaft. More recently, it has been considered to employ planetary gearsets in the power flow paths downstream of the dual input clutches.
It is an object of present invention to provide an improved dual input clutch power transmission employing planetary gearsets.
In one aspect of the present invention, the transmission includes a compound planetary gearset and a Ravigneaux planetary gearset.
In another aspect of the present invention, the Ravigneaux-type gearset is comprised of a simple gearset and a compound gearset.
In still another aspect of the present invention, a plurality of synchronizers is disposed between the input clutches and the planetary gearsets.
In yet still another aspect of the present invention, a synchronizer clutch and brake mechanism are employed in series to provide reaction members in the second planetary gearset.
In a further aspect of the present invention, a second brake mechanism is included to establish another member of the second planetary gearset as a reaction member.
In a yet further aspect of the present invention, one member of the first planetary gearset and one member of the second planetary gearset are continuously interconnected and are also continuously interconnected with an output shaft of the transmission.
In a still further aspect of the present invention, a total of five mechanical or synchronizer clutches are employed, four of which provide two-way clutching operations and one of which employs a one-way clutching operation.
In a yet still further aspect of the present invention, two of the mechanical clutches are considered configuration clutches which are employed to provide interconnections between the planetary gearsets as opposed to applying an input to the planetary gearsets.
In yet a still further aspect of the present invention, two of the synchronizer clutches provide input power paths from the input clutches to the planetary gearsets.
In another aspect of the present invention, one of the input mechanical clutches selectively connects one of the input clutches with two members of the first planetary gearset individually.
In still another aspect of the present invention, the second of the input synchronizer clutches provides an input connection between the other input clutch and two members of the second planetary gearset.
In yet still another aspect of the present invention, the first or compound planetary gearset is a three-node planetary gearset and the second or Ravigneaux gearset is a four-node planetary gearset.
The input clutches and synchronizer clutches are engaged in a plurality of combinations to provide at least six forward speed ratios and one reverse speed ratio. The combinations of engagements also provide up to nine forward speed ratios and a reverse speed ratio. This permits the transmission to provide various overall ratio coverage depending upon the usage of the transmission. The ratio coverage provided in even the six speed transmission, permits direct connection between the engine and the input clutches without the intervention of a hydrodynamic drive, such as a torque converter, thereby improving the overall efficiency of the transmission. It is considered that those skilled in the transmission art will be aware of the many electro-hydraulic control systems that are available to control mechanisms, such as input friction clutches, friction brakes, and synchronizer manipulation mechanisms.